Home value
You have almost certainly seen a number already. Here is what it is measuring, what it cannot measure, and how far out it is likely to be.
The short answer: if your home is not currently listed for sale, the estimate you are looking at has a published median error of roughly seven per cent. On a $600,000 home that is a $45,000 swing, and median means half of all homes are further out than that.
Both Zillow and Redfin publish their own error rates, and both split them the same way: homes currently listed for sale, and homes that are not.
| Published median error | Listed for sale | Not listed |
|---|---|---|
| Zillow Zestimate | 1.9% | 7.5% |
| Redfin Estimate | 1.9% | 7.4% |
| On a $400,000 home | $7,600 | $30,000 |
| On a $600,000 home | $11,400 | $45,000 |
| On a $900,000 home | $17,100 | $67,500 |
Source: Zillow and Redfin published accuracy figures, nationwide medians, 2026. Dollar figures are the median error applied to the price shown. Median means half of all homes fall further out than the figure given.
If you are reading this, your home is almost certainly not listed. You are looking at the second column.
Accuracy is scored against the most recent estimate before the sale, not the estimate from six months earlier when a homeowner was deciding whether to sell.
And when a home goes on the market, the estimate tends to move toward the list price. Which means the strong on-market figure is partly measuring how closely the model tracked a number an agent had already set, after the market had already corrected it.
The off-market figure has no such correction. It is the one to judge by, and it is the one describing your home right now.
An automated valuation reads public records, tax assessments and past listings. Zillow states in its own FAQ that unreported additions, updates and remodels are not reflected. So the list of what it misses is not a criticism, it is a description.
The kitchen taken back to the studs in 2023, if nobody pulled a permit.
Which side of the street floods, when the line runs between two identical rows of houses.
The sale two doors down that was between family and never reached the open market.
A roof replaced last spring, or one at the end of its life.
Whether the comparable sale down the road was renovated or sold as-is after a death in the family.
Every one of those moves the price, and a local agent who has been inside the house knows all of them. The question is whether they put it on the page.
The document that answers this properly is a comparative market analysis. Any agent will produce one. Four questions separate the ones worth reading.
A set of five clean sales and nothing else has been collected rather than selected. Every real analysis rejects some. Ask which, and why.
A comparable with an extra bathroom is not your home. The adjustment should be a dollar figure with a reason beside it, not a feeling.
A single confident figure hides how much the evidence disagreed with itself. A range shows it. Ask how wide it is and what would narrow it.
This is the question the whole page is about. If the answer is not written down anywhere in the document, it will not be there when a buyer's agent argues the price.
An example of what that document looks like when the working is shown, on a fictional home with illustrative data.
It depends entirely on whether the home is currently listed for sale, and the difference is large. Zillow publishes a nationwide median error of about 1.9% for on-market homes and about 7.5% for off-market homes. Redfin publishes about 1.9% and about 7.4%. A homeowner checking their own value is almost always off-market, which means the number they are looking at is the less accurate of the two. On a $600,000 home, a 7.5% median error is a $45,000 swing in either direction, and median means half of all homes are further out than that.
Partly because it has already seen the price an agent set. Accuracy is measured against the most recent estimate before the sale, not the estimate from six months earlier, and when a home is listed the estimate tends to move toward the list price. So the impressive on-market figure is measuring a number that has already been corrected by the market it is being scored against. The off-market figure has no such correction, which is why it is the honest one to judge by.
Anything that is not in a public record. A renovation nobody permitted. Which side of the street floods. A sale two doors down that was between family and never reached the open market. Whether the kitchen was taken back to the studs in 2023 or painted in 2011. Zillow states plainly in its own FAQ that unreported additions, updates and remodels are not reflected. Those are exactly the things that decide what a buyer pays.
No. Use it as a starting point and nothing more. Price it high against the market and it sits, gathers days on market, and takes a price cut that is visible to every buyer. Price it low and the money is gone at the closing table. Both mistakes are made by treating a single confident number as though it were an answer.
A comparative market analysis, and specifically one where you can see the working. Ask which comparable sales were used and which were considered and rejected, and why. Ask what dollar amount was added or subtracted for each difference between those homes and yours, and on what basis. Ask for a range rather than a single figure, and ask what would narrow it. An agent who can answer those four questions has done the work. An agent who cannot has given you a number.
If you are the agent
Then bring the document that answers it. CMAflow is a notebook for the listing side of your business: you write what you know about the house in plain language, and it reaches the analysis, the follow-up and the report the seller reads, under your name.
Every comparable adjusted toward this home with the reason printed beside the dollar. The sales that do not belong shown and set aside rather than quietly missing. A range earned by how tightly the evidence agrees, not chosen.